Gas-filled bushing with spring bias clamping and internal flexible shunt

ABSTRACT

A hollow insulation column has a central conductor extending therethrough, and the insulation column is filled with a highpressure gas, such as sulfur hexafluoride, under greater than atmospheric pressure in order to provide insulation between the central conductor and a centrally disposed mounting flange in the bushing. One end of the central conductor is connected to an end conductive plate of the bushing through flexible shunts in order to permit dimensional changes between the central conductor and the insulation bushing, due to temperature changes. The insulator is held clamped together by a spring biasing arrangement connected to the upper end of the bushing between a flange mounted on the upper end of the conductive member within the bushing and a plate which is fastened directly to the upper conductive head of the bushing. There are only two seals to the external atmosphere.

United States Patent 2,623,919 12/1952 Bowers 2,853,538 3,331,918 7/1967 Sonnenberg et al.

Inventor James R. McCloud Burbank, Calif.

Appl. No. 852,534

Filed Aug. 25, 1969 Patented Feb. 23, 1971 Assignee I-F-E Imperial Corporation Philadelphia, Pa.

GAS-FILLED BUSHING WITH SPRING BIAS CLAMPING AND INTERNAL FLEXIBLE SHUNT 4 Claims, 3 Drawing Figs.

9/1958 Frakes...

Primary Examiner- Laramie E. Askin Attorney-Ostrolenk, Faber, Gerb & Soffen ABSTRACT: A hollow insulation column has a central conductor extending therethrough, and the insulation column is filled with a high-pressure gas, such as sulfur hexafluoride, under greater than atmospheric pressure in order to provide insulation between the central conductor and a centrally disposed mounting flange in the bushing. One end of the central conductor is connected to an end conductive plate of the bushing through flexible shunts in order to permit dimensional changes between the central conductor and the insulation bushing, due to temperature changes. The insulator is held clamped together by a spring biasing arrangement connected to the upper end of the bushing between a flange mounted on the upper end of the conductive member within the bushing and a plate which is fastened directly to the upper conductive head of the bushing. There are only two seals to the external atmosphere.

GAS-FILLED BUSHING WITH SPRING BIAS CLAMPING AND INTERNAL FLEXIBLE SHUNT BRIEF DESCRIPTION OF INVENTION This invention relates to insulation bushings of the type used for bringing an electrical conductor into an enclosed housing, such as a gas-insulated circuit'breaker, and more particularly relates to a novel gas-filled bushing which is held assembled by virtue of a spring-biased connection and in which the central conductor of the bushing is connected to the terminal head of the bushing by flexible conductors, whereby only two seals are needed to the external atmosphere.

THE PRIOR ART Gas-filled bushings are well known for introducing high voltage conductors into a housing, such as a gas-filled circuit interrupter. It is necessary to construct such bushings so that at least the portion of the bushing extending beyond a sealed housing will itself be sealed to prevent the leakage of gas therefrom. In the past, up to six seals were needed. In addition, it is necessary to permit relative expansion or dimensional change between the central conductor of the bushing and the exterior dielectric housing. To this end, a. flexible bellows is commonly introduced between the interior diameter of the hollow insulation column and the central conductor where the bellows forms a gastight seal to the insulation column and permits relative expansion and contraction of the central conductor and the exterior insulator. The present invention eliminates the use of such bellows-type devices which are expensive and are subject to failure. Devices of this type are shown typically in the US. Pat. to Friedrich et al. No. 3,059,044. In particular, and in accordance with the invention, the bellows of the prior art is replaced by a flexible shunt extending directly from one end of the central conductor of the bushing to the main conductive head of the insulator. The main conductive head is then sealed to the en'dofthe insulation column by a novel spring clamping arrangement which clamps together the entire insulation column.

BRIEF DESCRIPTION OF THE FIGS.

FIG. 1 is a partial cross-sectional diagram of an insulation bushing constructed in accordance with the present invention.

FIG. 2 is a plan view of the flange member of FIG. 1 which is connected to the upper end of the bushing conductor.

FIG. 3 is an enlarged cross-sectional view of the filter arrangement in the conductive headplate of FIG. 1.

DETAILED DESCRIPTIONOF THE PREFERRED EMBODIMENT gas circuit interrupter. Thus, the entire section 11 will be immersed within such an enclosure, which may also be gas-filled.

Relatively hard, load-supporting gaskets l6 and 40 may, therefore, be provided'between the flange plates 12 and 32 and insulator section 11 to protect the insulator from damage by coming into contact with these metal plates, since leakage at this joint is allowable since both the interior of the tank 15 and the interior of the insulation column could both be filled I with gas at the same pressure.

The insulation section 10, however, is positioned above the exterior of the tank 15 so that an extremely effective seal must be provided between the flange plate 12 and insulator 10. This seal is shown in FIG. 1 as consisting of a relatively hard, loadsupporting compression gasket contained within suitable soft, sealing stop gaskets 21 and 22. The insulator bushing of FIG. 1 then contains a main elongated conductor 30 which is threaded into a conductive adapter 31 which is received by the conductive head plate 32. Electrical equipment within the housing 15 which are to be connected to conductor 30 are connected thereto through a suitable threaded connection, for example, with the adapter 31.

Note that the end of conductive tube 30 is provided with a filter disc 33 which is contained between the threaded clamping discs 34 and 35 which are threaded into the interior of the end of tube 30 to filter gases used to purge the interior of the bushing.

Conductive plate 32 is also provided with an opening 36 which is covered by a filter 37, as shown in FIG. 3, where filter 37 is held in place by screw 38 and gasket 39. This structure is useful for removing condensed moisture from the inside of the bushing. i

The outer end of the insulation bushing, as shown to the left in FIG. 1, contains a well-contoured end conductive plate 41 which may have a threaded terminal 42 extending therefrom so that convenient connection may be made to the bushing. Conductive member 41 is then sealed to the left-hand end of hollow insulator section 10 by a good pressure seal consisting of the hard, load-bearing compression gasket 43 and its relatively soft, sealing stop gaskets 44 and 45. It will be noted that the left-hand end of conductor 30 is spaced from conductive member 41 so that the conductor 30 may expand and contract at a different rate than insulator sections-l0 and 11, due to temperature change.

Electrical connection between conductive member 41 and the central conductor 30 and the means for holding the insulator assembled constitute the novel features of the present invention. This equipment includes a spring-receiving disc 50 and a conductive flange member 51 which is threaded onto the left-hand end of conductor 30. Flange member 51 is shown in plan view in FIG. 2. It will-be noted that flange member 51 has a threaded interior 52 which is threaded onto the end of conductive tube 30 and then fixed in this position by pin 53 which extends through a suitable opening in the upstanding wall 54, shown as opening 55 in FIG. 2, to prevent subsequent rotation of the flange member 51 with respect to conductor 30 after the bushing has been assembled.

Electrical connection is made between conductive member 40 and flange plate 51 and thus conductor 30 by means of flexible, conductive straps. These flexible, conductive straps may be packages of thin, copper sheets, for example, 25 layers of copper sheets, each having a thickness of 0.010 inch. A typical flexible conductor of this type is shown in FIG. 1 as flexible conductive member 60. A plurality of such flexible member will be distributed around the periphery of flange member 51, and, for example, either such conductive strips can be used, only one of which is shown in FIG. 1 for purposes of clarity.

, One end of the conductive members, such as conductive member 60, is bolted to the interior of conductive member 41 as by the bolt 61, while the other end envelopes around the exterior of the flange as shown, and is disposed beneath a pressure washer 62. Note that conductive member 60 may have an opening therethrough for passing a threaded insulated shank 63 which serves as a spring guide for the parallel springs 64 and 65. One end of spring 64 and 65 bears on pressure washer 62 in order to make good electrical contact between conductor 60 and flange 51. The other ends of springs 64 and 65 rest on insulated washers 100 which are carried on disc 50 as shown. Note that parts 63, and are insulated to prevent the various springs and bolts from carrying current and sparking to parts 50 and 51.

As mentioned above, a plurality of such assemblies are disposed about the flange member 51 where FIG. 2 illustrates an opening 70 for threadably receiving threaded shank 63, with the entire assembly of springs 64', 65, shank 63 and conductor 61 being associated with this portion of the cross-sectional view.

Seven similar assemblies will be similarly associated with threaded openings 71 to 77, shown in FIG. 2, for receiving the threaded shanks of the respective assemblies.

Spring-receiving disc 50 is then rigidly threaded into engagement with conductive member 41 .as by insulated bolts such as bolt 80, shown in FIG. 1. Note that bolt 80, along with seven other bolts in the preferred embodiment of the invention, will also pass through aligned openings in flange member 51, these openings being shown in FIG. 2 as through-openings 81 to 88. g

It will be observed that the springs, such as springs 64 and 65, will serve to hold the entire insulator bushing in mechanical alignment, with the insulator sections and 11 being in compression. That is, springs 64 and 65 are compression springs which urge members 50 and 51 away from one another. This has the effect of pressingconductive end members4l and I toward one another, thereby applying forces tending to hold the bushing assembled and applying pressure to the various seals throughout the assembly. At the same time, a strong pressure connection is made between flexible conductive strap 60 and the flange 51 to establish a good path for electrical current from conductive member 41 through the flexible conductors to conductive, flange 51 and thence through conductor 30 to the adapter 31. I

It will be observed that if there; should be dimensional changes of conductor 30 with respect to the insulator housings 10 and II, these dimensional changes will be easily absorbed by the flexible conductors, suchas conductor 60, without danger of cracking, while a good pressure seal is maintained throughout the interior of the insulator for those portions of the insulator bushing which are above the housing 15.

Although this invention has been described with respect to particular embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and; therefore, the scope of this invention is limited not by the specific disclosure herein, but only by the appended claims;

lclaim:

l. A gas-filled bushing comprising, in combination:

a hollow, elongated insulator column;

b. an elongated conductor within said hollow, elongated insulator column and extending along the axis thereof;

0. first conductive member positioned at one end of said insulator column and rigidly connected to one end of said elongated conductor;

d. a second conductive member positioned in fixed relation to the other end of said insulator column and forming a hermetic seal to said other end of said insulator column; said other end of said elongated conductor being spaced from said second conductive member;

e. means making a flexible electrical connection between said second conductive member and the other end of said elongated conductor, and including a flange member connected to said other end of said elongated conductor and flexible shunt means extending from said second conductive member to said flange member;

means clamping said first and second conductive members to said ends of said insulator including a pressure plate fixed to said second conductive member and disposed within the interior of said hollow insulator and disposed on the side of said flange member opposite to said second conductive member, and a spring-biasing means connected between said flange member and pressure plate for biasing said flange member and pressure plate away from one another; and

g. a high dielectric gas under greater than atmospheric pressure filling the interior of said hollow insulator.

2. The bushing of claim 1 which includes a mounting flange extending from the outer surface of said insulator column.

3. The bushing of claim 2 wherein said hollow insulator consists of first and second sections in'end-to-end disposition; said mounting plate comprising an annular member interposed between the adjacent ends of said first and second sections.

4. The bushing of claim 2 which includes first and second seal ring means respectively sealing said second conductive member to one end of said first section and sealing one surface of said mounting plate to the opposite end of said first section. 

2. The bushing of claim 1 which includes a mounting flange extending from the outer surface of said insulator column.
 3. The bushing of claim 2 wherein said hollow insulator consists of first and second sections in end-to-end disposition; said mounting plate comprising an annular member interposed between the adjacent ends of said first and second sections.
 4. The bushing of claim 2 which includes first and second seal ring means respectively sealing said second conductive member to one end of said first section and sealing one surface of said mounting plate to the opposite end of said first section. 